%/**
%Focus-vector computation
%@param alpha - elevation, scalar, rad
%@param beta - azimuth, scalar, rad
%@return H - focus-vector
% relevant to antenna's center, 7x1, rad
%*/
function Hv = H( alpha, beta )
k = [cos(alpha)*cos(beta); % Unit vector
        cos(alpha)*sin(beta);
                  sin(alpha)];
              
r{1} = [0 0 0];  % Antenna's radius-vector, in lambdas
r{2} = [1/2 0 0];
r{3} = [1/4 -sqrt(3)/4 0];
r{4} = [-1/4 -sqrt(3)/4 0];
r{5} = [-1/2 0 0];
r{6} = [-1/4 sqrt(3)/4 0];
r{7} = [1/4 sqrt(3)/4 0];

phi = nan(7,1);
for i = 1:7
phi(i) = 2*pi * r{i} * k;
end
Hv = exp( 1i * phi );
end